Electric furnace.



C. H. vom BAUR.

ELECTRIC FURNACE. APPLICATION FILED AUG.6. 1917.

1,252,633. A Patented Jan. 8,1918.

To all whom/it may concern STATES, PATENT orio.

CARL HANS VOM BAUR, OF DOUGLASTON, .NEW YORK.

. ELEcTnIc Fimivmsn.

Be it known that l, CARL HANs VOM BAUR, a lcitizen of the United States, and a resident of, Douglaston, in the county of Queens and State of New York, have, in'

vented certain new and useful lImprovements y in Electric Furnaces, of which the following is a specification. @i

Myinvention relates 4to -electric furnaces, and hasv for its object to provide a simple and efficient construction insuring a uniform lor approximately uniform distribution 0f the current, or of the heat produced thereby. The form of my invention illustrated herein and described in detail below, has especial reference to an electric furnace having an imperforate bottom and provided with electrodes connected .with a two-phase, threewire system` of electric current distribution,

all combined so as to secure certain advantages specifled hereinafter., Other features ofthe invention have reference to the adjustment of the electrodes, the shape of the furnace, and'various novel arrangements explained below and particularized in the appended claims. p

' In the accompanyingdrawing;

' Figure 1 is a vertical section online 1-1 Fig. 2, Ashowing a typical form of my improved electric furnace, witha diagram of its electrical connections;

Fig. 2,a plan" view of the furnace, with the roof removed;`

Fig. 3, a vertical section on line 3-3 Fig. 2; and c Fig. 4, an enlarged detail showing one of the adjustable electrodes'.

A1 l A, I have indicated a transformer whereby a polyphase Current su plied current to be supplied through the threev of the electric furnace.

through threewires (say'from an or inary alternator) is converted into. a two-phase wires B, B1, B2, to the electrodes C, C1, C2, Of` course, if a three-wire, two-phase current giving the desired furnace voltage is available directly,

the transformer A will not be required.

The electrodes pass through the top or roof D of the electric furnace, made of any suitable vrefractory material.' While preferably the electrodes are employed in a ver-` tical pesition, arrangements may be pro# vided forV adjusting them or at least the lateral electrodes C, C2, so thattheir lower ends will be brought nearer to, or farther from the sidewall E1 of the furnace, which side wall SpecicationJof'Letters Patent.

Patented Jan. 8, 1918.

` 4applicati@ mea August s, 1917. serial No. 184,554.c

is generally made integral with the solid (imperforate) bottom E. The central elec- `trode C1 is preferably adjustable only up and down, so thatl it is always vertical. For

" the purpose of such adjustment, the lateral electrodes pass through holders F of tubularl structure, with washers G of asbestos or'like material to secure the electrodes in the holderS.

Thes washers are required because al direct fitting of the electrodes to the holders is impossible on account of the lack of uniformity in the diameter of the electrodes as made commercially. The holders F are `made with surfaces F1 of` spherical. curva-4 ture, seated in corresponding" sockets at the outer ends of the roof openings-,through which the electrodes extend. "Suitable'frods or handles F2 may project upwardly from l the holders F, for adjusting thern as desired.

Thus the upright electrodes may' be., given either a perfectly vertical position asshown "on the left in Fig. 1, or one inclined in any direction, at the operators choice, as shown on the right in Fig.1. The electrodes are.

also adjustable lengthwise in their holders F.

The furnace is provided witha discharge "spout H (say at the middle of one of its furnace such a shape with reference to the normal locationl of the electrodes, C1, 02, that the amountsof heat reaching the s1d e wall when the mass within the furnace 1s molten, will be approximately the same forA every point of the contour of the side wall. For this purpose, as shown best in Fig. 2, the three electrodes are arranged normally -in the same plane, and the distances from vthe lower ends of the electrodes (when in their normal vertical position) `to the respective nearest points l'of the side wall E1, are exactly or approximately in the same ratio as the amounts of current received by the respective electrodes; that is to Say, ift-he distance from one of the lateral electrodes C, C2 to the nearestl point ofthe wall E1 is taken as 1, then the distance from the central electrode()1 to the nearest point of the side wall Ewill be 1/5, (slightly modi- 5 lied for the reason that the. heat rays from Iall three electrodes converge.) The outline required theoretically would be twopcircular arcs at the middle of the furnace, having their common center at Cl and 1/2 as their radius modified as described, these arcsbel ing continued to their points of intersection, y

as indicated by dotted lines in Fig. 2. In practice, however, this shape is modified by placing between said circula arcs, straight wall portions which are pre erably tangential to the respective arcs connected by them. With this arrangement, the distribution of the electric current and therefore the lheating effect (temperature-gradient) are prac- @tically 4uniform throughout the marginal portion'of'the `furnace, and all portions of lthe outline or periphery of .the side wall E1 will be heated approximately to the same extent, thus In the operation of my improvedvfufrnace it is intended to have theelectrodesextende I to the mass of material under treatment,sol I thatithe conducting molten bath will form part of the circuit between the electrodes.

It is\ by no means desirable .or thought advantageous to operate the phases separately, nor to arrange the electrodes in such a way that the heaty is generated; between ""5 ythe tips ofthe electrodes only, without the as hereinafterset fdrth."

aid of the .bath as .a' conductor for reasons The reason for not desiringthe arc to be' made only between the tips of the electrodes,

o which could be done y,hy\iiclining the two lesser current carrying electrodes C, C2, when arranged in a straight line2 or nearly so, and keeping the middle heavier current carrying electrode C1 vertical, is becausethis so-called free burning or flaming arc has been found detrimental to a prolonged life of the refractory materials in the side wall El andthe roof D. I do no-t wish the phases to be separate, since this would necessitate adding an electrode and would make the current unsteady on account of the lack of connection between the phases, and alsov since, in this case, each electrode, only carries, other things being` equal, the same amount of current, and, therefore, no predominatingly high current can be forced linto a highly piled up mass of raw material to be treated directly beneath the center" electrode.

My invention contemplates using, there fore, three electrodes all arranged vertically or nearly so, and adjustable not only inthe line of their axes,vbut also 'at an angle so that coldcorners of the metal, composition or other material. to be melted, can be avoiding uneven `temperature 5 strains.

.. and coul reached` by changing the position of one of the lesser carrying electrodes C, C2 to an angle from the vertical. Furthermore, by placing the electrode C1 carryingv the geometrical sum of the currents of the other two, in the center of the furnace and over --the cold material to be melted and treated,

which isl commonly piled higher in the cen ter than near the ends of the furnace, I secure the manifest improvement of having more current where the charge is heavier. Later on, when the charge is mol-ten, the heavier current and consequently greater heat of the electrode C1 carrying the greater current, as before mentioned, will materially .aid the circulation of the bath by making the part immediately beneath this larger current carrying electrode hotter than the parts of the molten bath beneath either of the'other electrodes carrying lesser currents. This is particularly so, when'the electrodes are arranged in a straight line, or nearly so, and this is the preferredconstruction of my invention. I do not, however, limit myself. theb electrodes in this manner,

to placin place them in a position so that they would be equidistant .from each other.

In prior constructions, the refractory side walls, particularly, have suffered severely from the radiated heat ofthe arc and it is the object withl this constructionv to mitigate this as much as possible 'by having as one, and the preferable form of hearth, the

. shape of an oval as shown inthe drawingv so that the greater, heat of' the central electhan the lesser heat of either of the other two electrodes, and the heat from each electrode is practically proportional to the'distance it 1s away from the 'side wall. Furthermore, this oval construction @gives a for the` same holdingcapacity and consequently, other things', being equal, themetallurgical treatment is hastened with my form of hearth or furnace, since thel slag contact with `the bath for an equal volume 1s greater and the refining of metals, such as iron or steel or the like, depends largely on the quantity of slag in contact with the metal to be treated. a

l In the form illustrated, my invention may therefore, be described as applied to an electric furnace of the arc type, the elec- `-trodes of which are specifically connected to ltrode is `farther away from the ,side walls greater areaof the bath than a', frou'nd form trode is so placed that the arc is between one end thereof 'and the material to be treated in the furnace, In this form, the main iuctuations will be found in the electric conductors and their directly connected electrodes C, C2 carrying the lesser currents, consequently, the remaining electrode C1 has fewer iiuctuations, which is of decided advantage, not only in maintaining a more uniform `heat in the furnace, but also in putting a lesser strain on the source of the electrical supply. The efliciency of the furnace is also increased since the heat gradient is the same in all parts of the furnace, (due to the position of the three vertical "electrodes, when in one line or nearly so,

placed in an oval shaped hearth, as herein mentioned) and because the heat is applied more uniformly even without the aid of eX- traneous means of automatic regulation of the electric heat.

I claim:

1. In an electric furnace, the combination of a two-phase, three-wire circuit, three upright electrodes connected to this circuit, a furnace having a solid bottom and an ovalshaped side wall of refractory material, said electrodes being so spaced that at the slag line the heat gradient is the same for each electrode at the point of the side wall which is nearest to such electrode.

2. An electric furnace whose outline, in plan view, comprises two end portions curved according to arcs of circles of equal' radii but diHerent centers, and two-middle portions curved according to arcs of a circle of greater radius having its center in line with the centers of the other arcs.

3. An electric furnace whose outline, .in plan view, comprises two end portions curved according to arcs of circles of equal radii but different centers, two middle portions cnrved according to arcs of a circlev Whose radius is substantially 1[j times the radius of either of the end arcs, and whose center is in line with those of the end arcs, and tangential portions connecting the middle arcs with the end arcs.

An electric furnace whose outline, in plan view, comprises a plurality of circular arcs having different centers, and electrodes located approximately at the centers of said arcs.

5. An electric furnace whose outline, in plan view, comprises two end portions curved according to arcs .of circles of equal radii but different centers, and two middle portions curved according to arcs of va circle of greater radius having its center in line with the centers of the end arcs, and electrodes located approximatelysat the centers of said arcs.

6. An electric furnace whose outline, in plan view, comprises two end portions 'curved according to arcs of circles of equal radii but different centers, two middle por,-

tions curved according to arcs of a circle Y whose radius is substantially JE times'the radius of either of the end arcs, and whose center is inline with those of the end arcs,

and electrodes located approximately at the centers of said arcs and adapted for connection with a two-phase, three-wire current supply.

CARL HANS VOM BAUR. 

